1. Field of the Invention
The present invention relates to a remote controlled actuator assembly for use in medical and machine processing fields and capable of changing the attitude of a machine tool.
2. Description of Related Art
Remote controlled actuator assemblies are currently available; some are used in the medical field for osteal treatment and some are used in the mechanical processing field for drilling and cutting. Any of those remote controlled actuator assemblies controls by remote control a machine tool fitted to a distal end of an elongated pipe of a linear or curved configuration. However, since the conventional remote controlled actuator assembly is designed solely to control only the rotation of the machine tool by remote control, difficulties have been encountered in processing of a complicated shape and processing at a site difficult to view with eyes from the outside in the medical field. Also, in the drilling process, the capability of processing not only the linear line, but also the curved configuration is often required. In addition, in the cutting process, the capability is required to perform the process at a site deep in grooves. In the following description, conventional art and problems inherent in the remote controlled actuator assembly will be discussed with reference to the medical field.
In the orthopedic field, the artificial joint replacement is well known, in which a joint, of which bone has been abraded by due to bone deterioration, is replaced with an artificial joint. The joint replacement surgery requires a living bone of a patient to be processed to enable an artificial joint to be implanted. In order to enhance the strength of postoperative adhesion between the living bone and the artificial joint, such processing is required to be performed precisely and accurately in conformity to the shape of the artificial joint.
By way of example, during the hip joint replacement surgery, a thigh bone is opened to secure access of an artificial joint into the femoral marrow cavity. In order to secure a strength of contact between the artificial joint and the bone, surfaces of contact of the artificial joint and the bore must be large and so the opening for insertion of the artificial joint is processed to represent an elongated shape extending deep into the bone. As a medical actuator used in cutting the bone in a manner described above, the actuator is known, in which a tool is rotatably provided in a distal end of an elongated pipe and, on the other hand, a drive source such as, for example, a motor is mounted on a proximal end of the pipe so that the tool can be driven through a rotary shaft disposed inside the elongated pipe. (See, for example, the Patent Document 1 listed below.) Since in this type of medical actuator a rotatable element that is exposed bare to the outside is only the tool at the distal end of the elongated pipe, the tool can be inserted deep into the bone. It is to be noted that as the actuator assembly for use in the medical field, which does not make use of the elongated pipe, an actuator assembly has also been known (such as disclosed in, for example, the Patent Document 2 listed below), in which a portion of the actuator where a tool is provided relative to another portion of the actuator that is gripped by hand can be altered in attitude.
The surgical operation for artificial joint replacement generally accompanies skin incision and muscular scission. In other words, the human body must be invaded. In order to minimize the postoperative trace, it is quite often desirable that the elongated pipe referred to above is not necessarily straight, but is moderately curved. To meet this desire, the following technique has hitherto been suggested. For example, the Patent Document 3 listed below discloses the elongated pipe having its intermediate portion curved twice to displace an axial position of the distal end of the pipe relative to the longitudinal axis of the proximal end of the same pipe. To make the axial position of the distal end of the pipe relative to the longitudinal axis of the proximal end of the same pipe is also known from other publications. Also, the Patent Document 4 listed below discloses the elongated pipe rotated by 180°.
If in a condition, in which the artificial joint is inserted into an artificial joint insertion hole formed in the living bone, a large gap exists between the living bone and the artificial joint, a large length of time is required to accomplish the postoperative adhesion between the living bone and the artificial joint and, therefore, it is considered desirable that the gap should be as small as possible. Also, it is important that respective surfaces of contact between the living bone and the artificial joint be smooth, and accordingly, a high precision is required in processing the artificial joint insertion hole. Whatever shape the pipe takes, the working range of the tool is limited by the shape of the pipe and, therefore, it is difficult to process the artificial joint insertion hole so that the living bone and the artificial joint may have smooth contact surfaces and, yet, the gap between the living bone and the artificial joint may be small while skin incision and muscular scission are minimized at the same time.
In general, it is quite often that the patient's bone, where an artificial joint is to be implanted, exhibits a strength lowered as a result of aging and, in a certain case, the bone itself is deformed. Accordingly, the processing of the artificial joint insertion hole is more difficult to achieve than generally considered.
In view of the foregoing, the applicant or assignee of the present invention has attempted to provide a remote controlled actuator assembly of a type, in which the attitude of the tool coupled to the distal end can be changed by remote control so that the processing of the artificial joint insertion hole can be relatively easily and accurately performed (see, for example, the Patent Documents 5 to 7 listed below). This is because if the attitude of the tool can be changed, the tool can be maintained at a proper attitude regardless of the shape of the pipe.